1. The Field of the Invention
The present invention relates to novel orthopedic casting materials, and in particular, to orthopedic casting materials and methods employing a nonwoven fabric.
2. The Prior Art
Many different orthopedic casting materials have been developed for use in the immobilization of broken or otherwise injured body limbs. Some of the first casting materials developed for this purpose involve the use of plaster of Paris bandages consisting of a mesh fabric (e.g., cotton gauze) with plaster incorporated into the openings and onto the surface of the mesh fabric.
Plaster of Paris casts, however, have a number of attendant disadvantages, including a low strength-to-weight ratio, resulting in a finished cast which is very heavy and bulky. Furthermore, plaster of Paris casts typically disintegrate in water, thus making it necessary to avoid bathing, showering, or other activities involving contact with water. In addition, plaster of Paris casts are not air permeable, and thus do not allow for the circulation of air beneath the cast which greatly facilitates the evaporation and removal of moisture trapped between the cast and the skin. This often leads to skin maceration, irritation, or infection. Such disadvantages, as well as others, stimulated research in the orthopedic casting art for casting materials having improved properties over plaster of Paris.
A significant advancement in the art was achieved when polyisocyanate prepolymers were found to be useful in formulating a resin for orthopedic casting materials, as disclosed, for example, in U.S. Pat. No. 4,502,479 (Garwood et al.). U.S. Pat. No. 4,502,479 sets forth an orthopedic casting material comprising a knit fabric which is made from a high modulus fiber (e.g., fiberglass) impregnated with a polyisocyanate prepolymer resin such as polyurethane. Orthopedic casting materials made in accordance with U.S. Pat. No. 4,502,479 provide significant advancements over the plaster of Paris orthopedic casts, including a higher strength-to-weight ratio and greater air permeability. However, such orthopedic casting materials tend not to permit tactile manipulation or palpation of the fine bone structure beneath the cast to the extent possible when applying a plaster of Paris cast. In this regard, knit materials are not as compressible as plaster, and tend to mask the fine structure of the bone as the cast is applied. Moreover, orthopedic casting materials involving knit fabrics such as fiberglass are somewhat expensive, and may be cost prohibitive for some users.
An example of an orthopedic bandage using a polyester fabric which is not a knitted fabric is disclosed in U.S. Pat. No. 3,972,323 (Boricheski). However, the orthopedic bandage disclosed in U.S. Pat. No. 3,972,323 involves the use of plaster of Paris, and thus is subject to the disadvantages outlined hereinabove for plaster of Paris orthopedic casts, including an inferior strength-to-weight ratio and poor air permeability.
From the foregoing, it will be appreciated that what is needed in the art is an orthopedic casting material which has both the advantages of plaster of Paris, e.g., good moldability and palpability of the fine bone structure, and the advantages of non-plaster of Paris materials, e.g., good strength-to-weight ratio and good air permeability. In this regard, it would be a significant advancement in the art to provide such a combination of advantages without actually using plaster of Paris, thereby avoiding the inherent disadvantages of plaster of Paris outlined herein. It would be a further advancement in the art to provide such non-plaster of Paris orthopedic casting materials which have as good or better properties than the non-plaster of Paris orthopedic casting materials of the prior art, and which can be made to be significantly less expensive, and therefore less cost prohibitive, than prior art orthopedic casting materials employing knitted fabrics. Such orthopedic casting materials and methods for preparing the same are disclosed and claimed herein.